Silencers for the exhaust gases of vehicle internal combustion engines



May 29, 1962 G. CALABRESI 3,036,653 SILENCERS FOR THE EXHAUST GASES OFVEHICLE INTERNAL COMBUSTION ENGINES Filed Dec. 4, 1957 //v YEN/*0 G/z/sEPPE CZLABRES/ United States Patent 3,036,653 SILENCERS FOR THE EXHAUSTGASES OF VEHICLE INTERNAL COMBUSTION ENGINES Giuseppe 'Calabresi, 19 ViaDei Daimati, Rome, Italy Filed Dec. 4, 1957, Ser. No. 700,706 Claimspriority, application Italy Dec. 6, 1956 Claims. (Cl. 181-44) My presentinvention relates to improvements in silencers for the exhaust gases ofinternal combustion engines usually employed in vehicles of all kinds,such as motor-cars, motorcycles, trucks, airplanes, motorboats, ships,and so on.

It is a well known fact that when the exhaust gases leave the cylinderof any internal combustion engine the pressure is still high e.g. ashigh as 3-4 atmospheres or even higher. When coming into contact withthe air, these gases expand rapidly and produce a series of louddetonations.

It is an object of my invention to avoid such drawbacks by the provisionof an improved silencer in the path of the exhaust gases of an internalcombustion englue.

The silencer according to my present invention is based on the findingthat a stream of exhaust gas can be divided by a single, improvedbafiiing unit into two flows of different density, of a phase oppositionsuch that the expension of the one corresponds to the compression of theother one, and as a consequence of this produces the desirable effectthat the sound waves produced by the engine travel in two mediums with aphase displacement in respect to each other as to speed, pulsations anddensity. In addition, and in order to transform this phase displacementinto interference, this baflling unit is provided with suitableopenings, through which both flows communicate.

I have additionally found that this phase displacement and thereby aperfect silencing action can be achieved by locating in a mufller casingtwo such units suitably arranged in respect to each other. An inherentadvantage of the silencer as per the present invention is that it causespractically no back pressure and thus eliminates losses in engineperformance.

This will become clear and substantiated in the following description ofmy invention, illustrated by the accompanying drawing, which representsa view, partly in longitudinal section, of the silencer, with onedividing and bathing unit being visible.

Referring now to the drawing, reference number 1 indicates an exhaustpipe provided in a series arrangement with an exhaust box 2 of anysuitable cross-sectional shape. The exhaust pipe is connected, at one ofits ends, to one or several pipes extending from one or several outletsof the cylinder or cylinders of an internal combustion engine not shown.At the opposite end of the exhaust pipe, the exhaust gases aredischarged into the atmosphere, after the detonations or noise of theexhaust have been muffied by one or several silencers according to theinvention.

In the following specification a single silencer will be described,arranged within the exhaust box of the exhaust pipe; however, it is tobe understood that more than one silencer may be installed Within thesame exhaust box and/0r along the exhaust pipe 1 of a smaller diameter.Good results may also be achieved by applying one or more silencersaccording to my invention, within an exhaust pipe not provided with anexhaust box.

According to the illustrated embodiment the silencer comprises a hollowbody 3 having a longitudinal or axial cross-section of approximatelyrhomboidal shape so that body 3 is formed by two opposite hollow conesconnected to one another at their bases. At the opposite vertices ofsaid hollow body two openings 4 and 5 of equal diameter are provided.Furthermore, the body 3 may be provided with slots or other openings 16through which its interior can communicate with the outer space betweenthe body and the inner cylindrical surface of the exhaust box 2. Thehollow body 3 is preferably (but not necessarily) secured coaxially withand interiorly of the exhaust box 2 by means of a transverse supportingwall 6 which, in the embodiment shown, has a frusto-conical shape withthe edge 7 of lesser diameter facing the outlet end of the exhaustpipe 1. The edge 7 is spaced from the peripheral surface of maximumdiameter of the hollow body 3 and may be fastened to said peripheralsurface of the hollow body 3 e.g. by means of spots of welding material8. The edge 9 of greater diameter of the supporting wall 6 contacts theinner surface of the exhaust box 2 and is fixed thereto by any suitablemeans, e.g. by a continuous welding.

The exhaust gases, leaving the outlets of an internal combustion engine,gather in the form of a single gaseous current within the exhaust pipe 1and the exhaust box 2, until they reach the open front end 4 of thehollow body 3. At this point, the single gaseous current divides into aninner current (indicated by arrow 10) entering the hollow body 3 and anouter current (indicated by arrow 11) flowing between the hollow bodyand the cylindrical wall of the exhaust box. The gases forming the innercurrent 10 will expand when they reach the zone of maximum diameter 12of the inner cavity of the hollow body 3, whereas the gases forming theouter current 11 will be compressed when they have to pass through theannular slot 13 formed by the edge 7 of lesser diameter of thefrusto-conical surface 6 and the surface of maximum diameter of thehollow body 3. Thus, an expansion of the inner current 10 and acompression of the outer current 11 occur simultaneously at an identicalzone or cross-section of the exhaust box 2.

These opposing and simultaneous actions on the two gaseous currentscause such phase displacements of the sound waves carried by thosecurrents that a noise muffiing zone or even a zone of silence will becreated at such cross-section of the exhaust box.

The inner current 10 is then under compression at the outlet 5 of thehollow body 3, while the outer current 11 is under maximum expansion atthe cross-section of the exhaust box 2 in the transverse plane of theoutlet 5. Hence, another simultaneous and opposing action on the gaseouscurrents 10, 11, i.e. a further deadening of the sound waves, occursowing to the last mentioned crosssection.

Another important fact is that, the currents of exhaust gases are notsubjected to any noticeable resistance by the hollow body 3 and thesupporting wall 6, so that the power loss of the engine is non-existentor nearly so. This result is confirmed in practice by the fact that theexhaust gases coming from the free end of the exhaust pipe, have still avery high temperature, contrary to what happens when conventionalsilencers are used. I have found that the provision of the slots 16 inthe hollow body 3 brings about an improved result and this is probablydue to the fact that the slots 16 allow a reciprocal mixing of the gasesof the two currents 10 and 11 while flowing. Thereby they prevent thesound waves which had been phase-displaced at the annular slot 13 frombeing restored to an in-phase relationship at the outlet 5 of the hollowbody 3.

While I have described a preferred form of silencer, it is to beunderstood that numerous alterations, modifications and changes in thedetails may be made in the silencer according to my present invention,without departing from the spirit and scope of the invention as definedin the claims which are made a part hereof.

What I claim is:

1. A silencer mounted in a conduit adapted to carry exhaust gases froman internal combustion engine and comprising a hollow, elongated bodyopen at its opposite ends to provide at said ends an inlet and outlet,respectively, for said exhaust gases, said body flaring from saidrespective ends to a location intermediate its ends so as to definewithin the body an inner gas expansion chamber progressively enlarged ina direction from the inlet to said location, and an inner gascompression chamber progressively decreased in a direction from saidlocation to the outlet, said inlet, chambers and outlet affording anunobstructed passage for a portion of the exhaust gases entering thebody through the inlet; and a 'baflie mounted between the conduit andthe body, said baifle surrounding said body between the inlet and saidlocation, said baflle tapering from the conduit toward said location,the conduit, flaring body and tapering bafile defining an outercompression chamber extending about and located in side-by-side relationto the inner expansion chamber, the conduit, the body and the b-aifledefining, downstream from the baflle, an outer expansion chamberextending about the inner compression chamber in sideby-side relationtherewith, said outer expansion and compression chambers communicatingthrough constricted exhaust gas passage means between the bafiie and thebody at said intermediate location of the body whereby to first producean expansion of gases flowing within the body simultaneously withcompression of gases flowing past the body exteriorly thereof, followedby a compression of the gases flowing within the body simultaneouslywith expansion of the gases flowing exteriorly of the body.

2. A silencer as in claim 1 wherein the larger end of the batlle isdisposed downstream from the inlet of the body.

3. A silencer as in claim 1 wherein the body is formed with a pluralityof apertures spaced longitudinally thereof and communicating between theinner expansion chamber and outer compression chamber.

.4. A silencer as in claim 3 wherein the body has additional openingsspaced longitudinally thereof and communicating between the innercompression chamber and the outer expansion chamber.

5. A silencer as in claim 4 wherein the several openings are formed asslots angul-arly spaced about and extending circumferentially of thebody.

References Cited in the file of this patent UNITED STATES PATENTS

